Matrixing can be carried out when transmitting a first main signal component (the left hand signal component L of a stereo signal), a second main signal component (the right hand signal component R) and an auxiliary component (a central signal component C), such that a first composite signal component L.sub.0 is obtained which equals L+a.C and a second composite signal R.sub.0 is obtained which equals R+b.C, and where the signals L.sub.0, R.sub.0 and C are transmitted. Upon reception by a standard receiver not being provided with a corresponding dematrixing circuit, the signal components L.sub.0 and R.sub.0 are used for supplying via two stereo loudspeakers to a listener. The listener is thus able to perceive the C component transmitted as well, although he has a standard receiver.
More sophisticated matrixing schemes are discussed in J.A.E.S., Vol. 40, No. 5, May 1992, pp. 376-382, as well as in the publication `Matrixing of bitrate reduced audio signals` by W. R. Th. ten Kate et al, in Proc. of the ICASSP, Mar. 23-26, 1992 San Francisco, Vol.2, pp. II-205 to II-208, documents (1a) and (1b) in the list of references, as well as document (8).
They all satisfy the requirement that, even if a 4-channel (R, L, C and S) signal, or a 5-channel (L, R, C, LS, RS) signal is transmitted, the transmitted signal can be decoded by a standard stereo receiver.
Compression means for bit rate reducing a signal has been described in published European patent applications 457,390A1 (PHN 13.328) and 457,391A1 (PHN 13.329), the documents (7a) and (7b) respectively in the list of references. Further, reference is made to two ISO/IEC standard documents, the documents (9) and (10) in the list of related documents, referred to as MPEG-1 and MPEG-2 standard documents respectively.